1. Field of the Invention
The present invention relates to a cooling technique of a belt-type continuously variable transmission device (CVT) and a muffler in a work vehicle having an engine and the belt-type CVT.
2. Description of the Related Art
With respect to the cooling technique of the belt-type CVT, Japanese Unexamined Patent Application Publication No. 2005-238988 describes a vehicle in which a body frame is provided with an engine, a belt-type CVT for changing a driving force of the engine, and a muffler connected to an exhaust pipe of the engine. In this patent document, the belt-type CVT has a transmission cooling system for sucking external cooling air from a feed duct; supplying the cooling air into a belt case to thereby cool the belt-type CVT; and sending this cooling air from the belt case through an exhaust duct to a rear part of a vehicle body. The exhaust duct and the muffler are arranged in parallel with each other in a lateral direction, and a discharge direction of a discharge port at a rear end of the exhaust duct is oriented to the muffler, to thereby lead the cooling air discharged from the discharge port to the muffler and to cool the muffler.
However, in a case where the discharge port at the rear end of the exhaust duct is oriented in the lateral direction of the vehicle body, when the vehicle body is running, an air flow from outside acts on the cooling air discharged from the discharge port. When the air flow from outside acts on the cooling air discharged from the discharge port, a position on the muffler on which the cooling air is blown is displaced rearward of the vehicle body and the cooling air discharged from the discharge port is diffused by the air flow from outside. As a result, an amount of the cooling air led to a surface of the muffler is reduced, and thus cooling performance is lowered.
Similar to the above-described prior art, Japanese Unexamined Patent Application Publication No. 2006-27425 describes a transmission cooling system for sucking the external cooling air from an intake duct; supplying the cooling air into the belt case to thereby cool the belt-type CVT; and sending this cooling air from the belt case through a discharge duct to the rear part of the vehicle body. The muffler and the discharge duct are parallelly arranged closer to each other. In this case, by positioning the muffler (object to be cooled) closer to the discharge duct (cooling means), an area around the muffler is effectively cooled.
However, even though the lowering in the cooling performance by the air flow from outside during the vehicle body running is suppressed, the cooling itself is not so efficient.